I think we’re all pretty much sold on the idea of wiring our houses for the future, but before we can run any cable, we’ll have to determine where the other end will go. This brings us to the wiring closet, also known as the home run point, wiring center, or in my wife’s terms: the geek closet.

The wiring closet exists to hold not only the ‘other end’ of the cables we run to various points in the house, but also the devices like network hubs, PBXs, alarm control panels, video and audio distribution equipment, etc. that will provide the services these cables carry. The cables themselves need very little space, or environmental concerns, but the active equipment will usually do best in a somewhat controlled or stabilized environment.

Before we can find a location for the wiring closet, or begin to plan it’s layout, a decision has to be made up front about how much you expect to enclose in it. If you only plan to house a PBX, alarm system, a bit of video distribution equipment, and maybe an IR or Ethernet hub then space and environment are of minimal concern. Once you decide to start adding home control PC’s, VCR’s for security recording, or whole-house amplifiers, then things like temperature, humidity, and airflow become more of a concern since these components usually expect a controlled humidity environment, and a somewhat stable temperature, preferably around 70degrees F. In most cases where your wiring closet is located in a basement, or garage, these requirements will most likely not be too difficult to satisfy. We’ll approach this months article with the assumption that your wiring closet will not require excessive attention to these criteria.

One of the main considerations is the wiring closet location and layout. Bear in mind that your wiring closet will contain not only a large bundle of incoming cables, but also patch panels for the various cables, and most likely several ‘active’ devices like PBX’s, network hubs, security equipment, etc. You’ll need to have an adequate power feed (a 20amp circuit will usually be sufficient), but also ventilation, depending on location of the wiring closet. For these reasons it’s usually best to dedicate your wiring closet to this purpose alone, rather then trying to ‘squeeze’ it into a coat closet, or other location. As enticing as it may be to have your wiring closet located in a high visibility place like your home office, or media room, I highly recommend that you locate in a non-obtrusive area. The next owners of your house will most likely see the value of a well designed structured wiring system, but the aesthetic value is sometimes an acquired taste.

Fortunately, you usually won’t need a very large area for your wiring closet. A 6’x6′ piece of floor space is usually more than enough to satisfy the needs of a better than average setup. Often times you’ll find the wiring closet under the basement stairs (when the house has a basement), or partitioned off from a utility room or garage. Things like PBX’s, hubs, and video distribution equipment can handle almost any environment. File servers, PC’s, VCR’s and similar devices with moving parts usually do best when the temperature remains fairly stable, around 60-80degrees F, and the environment is kept clean and free of lots of airborne dust. Humidity should be kept in the same range as the rest of the house.

Now that we have the basic environmental requirements established we can begin to layout our closet. Given that wiring closets usually occupy relatively small areas, the wall with the door is usually useless, leaving us three walls to work with, at best. If you can design it so that the door opens outward (assuming it’s enclosed) you’ll be able to make maximum usage of the interior space. With the remaining three walls, I usually like to divide them into three areas horizontally:

The upper area (1) will be used to mount things like alarm panels, HVAC controls, PBX’s, and similar devices that will require little or no intervention once they are installed. The middle area (2) will house cross-connects, things like patch panels, distribution panels, and automation controllers. These are the components you will be most likely to interface with. Area (3) is often unused because wiring closets tend to be in basements or garages, where there is often a risk of flooding or other water damage.

From here, the layout criteria are going to depend very much on the amount of space you have to work with, in an ideal situation there would be lots of free space between various components, allowing room for easy expansion in the future. In reality, though we often have limited amounts of space to work with. Keep the following things in mind when laying out and mounting equipment:

It’s quite common to end up adding an expansion cabinet to an alarm system to allow for zone expansion, relay boards, extra battery backup capacity, etc. Leave a space next to your alarm cabinet to allow for the mounting of an expansion cabinet.

If you are installing a PBX, leave room for a future voice mail cabinet, usually these are pretty small so, about 12″x15″ should be plenty.

If you are not installing a PBX, leave room to mount one in the future, plan for about 30″x18″ or so.

If your PBX is mounted sideways, so that the cards slide in/out parallel to the wall it’s mounted on, leave plenty of room in front of the cabinet for card access.

Ensure that there is adequate spacing between devices to allow for air-flow for cooling purposes. This is especially important for whole-house audio amplifiers.

Remember that most cables have a minimum bend radius, and this minimum tends to increase as the bundle diameter grows. A large bundle (20 cables or more) of coax will require about an 8″ diameter for a smooth curve. A large bundle of Cat5 cables will require about 6″ of diameter for a smooth curve.

Pay attention to things that swing or move, like PBX cabinet doors, alarm cabinet doors, and patch panel mounts, make sure they have room to travel without bumping into other devices.

Mount electrical outlets near the top of zone 1 and the bottom of zone2. The will help keep electrical cords from interfering with cabinet doors, and cables.

Using the tips and ideas outlined here you should be able to layout a functional and well-designed wiring closet. Next month we cover installing cable in a new construction home, with pictures of a cabling system I recently roughed-in. I’ll also include a list of tools and materials you’ll most likely need, and share some tips to make a one-man job a little easier.